The present invention relates in general to a needle guard of a sewing machine installed with a double lockstitch hook having a rotatably pivoted hook body, with hook beak and a needle guard, one end of which is fastened by screws to the rotating hook body.
In U.S. Pat. No. 1,917,771 a type of such needle guard or needle guide is described wherein a needle guide is fastened with two screws at the circumference of the hook body. The other end of the needle guard extends with its free end into the area of the hook beak to prevent the needle, while penetrating in the workpiece, from collision with the hook beak, and to guide the needle.
Due to manufacturing tolerances of the hook body at the needle guard itself, and depending on the size of the needle, the needle guide of this type must be adjusted. This is achieved by bending the needle guide. Such a procedure of adjustment requires some skill at which the polished area of the needle guard as well as the polished hook beak must be prevented from any damage.
Moreover, in U.S. Pat. No. 2,866,425 there is presented a rotating double lockstitch hook installed with an adjustable needle guard. According to the description, the needle guard is adjustably fastened with screws at the undersurface of the hook body. As the complete hook is installed in a sewing machine, the screws for adjusting the needle guard are not accessible. Due to this kind of mounting, it is necessary to perform the procedure of adjustment of the needle guard with respect to the hook beak prior to the installation of the complete hook in the sewing machine for which additional auxiliary tools, e.g. a dial gauge (mechanical indicator) are required. When adjusting a needle guard of such type, one has to take care not to alter the adjustment as the screws fastening the needle guard to the hook body are tightened. Moreover, the manufacturing of a needle guard of such construction requires some effort.
Accordingly, it is the main object of the present invention to provide a needle guard for a double lockstitch hook of a sewing machine, which is simple in construction and simple to adjust under actual operating conditions as the hook is installed in the sewing machine.
A further object of the present invention is to install a needle guard with elements which make possible a fine adjustment that is easily accessible in the machine.
Still another object of the present invention is to provide a needle guard for a double lockstitch hook with adjustment means, which allow to easily make re-adjustment of the needle guard with respect to the needle and the hook beak.
A still further object of the present invention is to provide a needle guard of the aforegoing character which may be manufactured at low cost and is reliable in operation.